The present invention is related to a mixing method and mixing apparatus, which ejects a gas for conditioning the physical properties of a material being mixed, such as the moisture content and temperature thereof. The mixing is conducted by stirring material having fluidity, such as fine particles and a granular material.
Japanese Examined Utility Model Publication HEI No. 5-36493 discloses a mixing apparatus, comprising a vessel of a material to be mixed; a rotating shaft provided to be drivable in a rotating manner around a horizontal axis inside this vessel; a stirring member provided so as to rotate together with the rotating shaft; an air jet provided on the stirring member; and a pulverizing member provided to be drivable in a rotating manner on the inner circumference of the vessel opposite the outer circumference of the rotating shaft. Air is ejected from the jet rearwardly of the direction of rotation of the stirring member to prevent the material being mixed from adhering to the inner circumference of the vessel.
However, with this prior art mixing apparatus, granulation and various chemical reactions cannot be properly performed by adding water and a reactive solution to the material to be mixed. For example, when performing granulation by adding water to the material to be mixed, it is believed that dry air ejected from the jet dries the material being mixed. However, with this prior art mixing apparatus, the dry air is ejected rearwardly of the direction of rotation of the stirring member. Since a space in the rear of the direction of rotation of the stirring member is created by forcing aside the material being mixed with the stirring member, the dry air and material being mixed cannot make contact in an efficient manner. Further, even if cooling air is ejected from the jet during an exothermic reaction caused by adding a reactive solution to the material being mixed, the cooling air and the material being mixed cannot make contact in an efficient manner. That is, because the air and the material being mixed cannot make efficient contact, the moisture content and temperature of the material being mixed cannot be efficiently conditioned.
Japanese Patent Laid-open SHO No. 51-61621 discloses a mixing apparatus, comprising a vessel of a material to be mixed; a rotating shaft provided to be drivable in a rotating manner around a vertical axis inside the vessel; a stirring member provided so as to rotate together with the rotating shaft; a jet, which ejects air upwardly from the center of the rotating shaft; another jet, which ejects air so that the air flows forwardly of the direction of rotation of the stirring member in a space above the material being mixed; and means for supplying a liquid to the inside portion of the vessel. Rotating the stirring member generates a vortex of air, which is ejected upwardly from the center of the stirring member. This swirling motion is enhanced by air, which is introduced so as to flow forwardly of the direction of rotation of the stirring member in the space above the material being mixed.
However, since the air flows in the space above the material being mixed, it only comes in contact with the surface of the material being mixed. That is, because the air and the material being mixed cannot make efficient contact, the moisture content and temperature of the material being mixed cannot be efficiently conditioned.
Great Britain Patent No. 1369269 discloses a mixing apparatus, comprising a vessel of a material to be mixed; a rotating shaft provided to be drivable in a rotating manner around an axis inside this vessel; a stirring member provided so as to rotate together with the rotating shaft; means for ejecting a gas for conditioning the physical properties of the material being mixed inside the vessel; a pulverizing member provided to be drivable in a rotating manner on the inner circumference of the vessel facing the outer circumference of the rotating shaft; and means for supplying a liquid to the inside of the vessel. A gas jet is provided at a fixed location relative to the vessel so as to enable the ejection of a gas from within the material being mixed during mixing.
However, with this prior art, nothing is disclosed concerning the direction in which a gas is ejected. That is, since no consideration is given to the air and the material being mixed making efficient contact, the moisture content and temperature of the material being mixed cannot be efficiently conditioned.
The object of the present invention is to provide a mixing method and mixing apparatus capable of solving the above-mentioned problems.
The mixing method of the present invention is characterized in that, when stirring a material being mixed with a stirring member, which rotates around an axis inside a vessel, a gas for conditioning the physical properties of the material being mixed is ejected forwardly of the direction of rotation of the stirring member from within the material being mixed during mixing.
The mixing apparatus of the present invention comprises a vessel for containing a material to be mixed; the rotating shaft provided to be drivable in a rotating manner around an axis inside the vessel; a stirring member provided so as to rotate together with the rotating shaft; and means for ejecting a gas for conditioning the physical properties of the material being mixed inside the vessel. A gas jet is provided in a fixed location relative to the vessel so as to enable the gas to be ejected from within the material being mixed during mixing. The gas is ejected forwardly of the direction of rotation of the stirring member.
According to the method of the present invention, a gas is ejected forwardly of the direction of rotation of the stirring member from within the material being mixed, during mixing, so that the residence time of the gas inside the material being mixed is lengthened, and thus the physical properties of the material being mixed is conditioned efficiently by the gas. The method of the present invention can be implemented with the apparatus of the present invention.
In the apparatus of the present invention, it is preferable that the rotating shaft is driven in a rotating manner around a horizontal axis; that the inner circumference of the vessel has a curved surface, which parallels a rotating body which is coaxial with the rotating shaft; and that the gas jet is arranged so that the ejected gas flows upwardly along the inner circumference of the vessel from the lower portion of the vessel.
According to this construction, even if the volume of the material to be mixed and stored in the vessel is much less than the capacity of the vessel, the residence time of the gas inside the material being mixed can be effectively lengthened, and the contact efficiency of the gas and the material being mixed can be enhanced.
It is preferable that the gas jet is constituted of an opening at the end of a pipe inserted into the vessel; that the end of the pipe is inclined relative to the horizontal plane so as to go rearwardly of the direction of rotation of the stirring member and in the downward direction; and the angle formed by the end of the pipe and horizontal plane of the pipe is less than the angle of repose of the powdered material to be mixed.
According to this construction, the material being mixed can be prevented from entering inside of the pipe.
It is preferable that a pulverizing member is provided to be drivable in a rotating manner on the inner circumference of the vessel facing the outer circumference of the rotating shaft, and that the location of the pulverizing member in the axial direction of the above-mentioned rotating shaft corresponds to the location of the gas jet in the axial direction of the above-mentioned rotating shaft.
According to this constitution, since the material being mixed can be made to flow toward the pulverizing member by the gas, the material being mixed can be pulverized more efficiently.
It is preferable that means for supplying a liquid to the inside of the vessel and a dispersing member which disperses the liquid supplied are provided, and that the location of the dispersing member in the axial direction of the above-mentioned rotating shaft correspond to the location of the above-mentioned gas jet in the axial direction of the above-mentioned rotating shaft.
According to this construction, causing the gas to flow to the location at which the liquid is supplied in a concentrated manner makes it possible to enhance the contact efficiency of the gas and the material being mixed in this liquid supply location. Therefore, the physical properties of the material being mixed can be efficiently conditioned, that is, dried and cooled, by the gas.
According to the present invention, it is possible to provide a mixing method and mixing apparatus, which are capable of efficiently conditioning the moisture content, temperature and other physical properties of a material being mixed by a gas.